What happens if too much or little shortening is used in pastry?

Depending on the type of flour you are working with, as well as the recipe, using too much flour can make your pastry too dense, tough or chewy. For example, if you are making a basic butter/shortening pie crust using all-purpose flour -- if you use too much flour or knead the dough excessively, you over-develop the gluten and will wind up with a tough crust vs. a light, flaky pastry.